Apparatus for solving seismographic problems



Oct. 15, 1940. J. F. ANDERSON 2,217,720

APPARATUS FOR SOLVING SEISMQGRAPHIC PROBLEMS I Filed Sept. 19, 1933 Patented Oct. 15, 1940 i v' 2 UNITED STATES PATENT OFFICE APPARATUS FOR SOLVING SEISMO- GRAPHIC PROBLEMS John F. Anderson, Beaumont, Tex., assignor to Sun Oil Company, Philadelphia, Pa., a corporation oi. New Jersey Application September 19, 1938, Serial No. 230,598

4 Claims. (Cl. 33-76) This invention relates to an apparatus for solv- Figure 2 is a vertical section taken on the ing graphically problems arising in seismographic plane indicated at 22 in Figure 1; and prospecting. Figure 3 is a vertical section taken on the plane In seismographic prospecting by the so-called indicated at 3-3 in Figure 1. I

5 reflection method a charge is set off at or near The device comprises a head formed of two 5 the surface of the ground and the arrival of reangles -2 and 4 joined by members 6 at their ends fiected waves is recorded by means of instruments and providing a slot 8 between them. The head located at varying distances from the shot. In thus formed is adapted to be located along the general, such work is carried out in a systematic edge of a drawing board indicated at 5. Slidably I 10 fashion so as to make the interpretation of results mounted within the channel formed by the mem- 1o comparatively easy and consequently rather well bers 2 and 4 are blocks Ill and I2, provided with defined arrays of the receiving instruments are bores arranged to receive a rod I4 of a length provided. For example, for the obtaining of one greater than the maximum spacing, on the graph, set of readings a line is laid out through the of the detecting stations. It may be noted that l6 location of the shot and the instruments are the head of the apparatus may be quite long so placed at evenly spaced intervals along such as to permit the construction of graphs of conline. Six instruments might be located at equal siderable size and that the rod I4, shown broken intervals over a spread of 2,000 to 3,000 feet for in Figure 1', may also be of quite substantial one shot and then the whole set moved further length.

2 along the line to equally spaced positions for The blocks may be locked to the rod 14 by succeeding shots. From the delays in times of means of set screws l6 and IS. The blocks are arival of characteristic impulses, which may be also adapted to be locked to the head by means regarded as reflections, as the distances from the of screws 20 and 22 extending downwardly shot point increase there may be deduced the apthrough the slot 8 and threaded into nuts 24 pro- 35 proximate depths of the reflecting boundaries and vided with squared shanks fitting within the slot '25 deductions may also be made of the probable 8 so as to prevent their turning therein. It will slopes of such boundaries. be obvious, therefore, that if the two blocks [0 To make proper deductions there is generally and I2 are secured to the rod [4 they may be slid first secured by refraction shooting, or by velocity lengthwise as a unit in the head upon release of measurements made in wells or by other methods the screws 20 and 22, and may be secured in any '30 known to those skilled in the art, a normal depth desired position by clamping oneor both of these velocity curve for the region so that, knowing the screws. The spacing between the blocks may be total delay between the time of the shot and the altered as desired by fr ing e S rews l arrival at one of the grouped instruments there and I3 and relatively Sliding e b s 0 t e may be deduced the approximate depth of the 36 reflecting boundary, Pivoted to the blocks l0 and 12, respectively, at

It is rather diflicult to make deductions of slope and 32 are arms 26 a e e ers of from the results thus secured, as will be obvious the o s 30 d 32 are eq l y sp ed from the from a consideration of the graphical construction e of e head which engages the dr rd which would have to be made to duplicate the and are, therefore, adapted to slide along a zero '40 results given by the instrument hereafter dedepth line indicated at I reference D scribed; and it is the object of the present inven- Poses notche? 1 and 35 9 Provided in the blocks tion to facilitate the graphical solution of the "P and to mdlcate accurately the Spread of the problem of determining the locations and slopes plvots and of the reflecting boundaries By the use of the The arms 26 and 28 are graduated as indicated improved apparatus, the results given by the 38 in terms of depth These arms may be of seismogmphs may be readily translated into a considerable length, suflicient to correspond to the deepest reflecting boundaries which may be exgraph of the boundaries.

pected to be considered. =0 The oblects of the mventmn Wm bfamme more Mounted on the arm 26 is a slide liladapted to apparent from the following description, read in be clamped in position thereon by means of a g r l il i With t e acco p y drawing in screw 42, and on the arm 28 there is a correv spending slide 44 adapted to be clamped thereto Figure 1 1s a plan view of the apparatus shown by a screw 46. These slides carry zero index '55 applied to the edge of a drawing board; markings 41 adapted to be read against the scales 38. The two slides are pivoted together by means of a bushing 48, preferably provided with a center hole in which there may be locateda pointed pin 50 which may be pressed downwardly to make a mark in the graph at desired times.

In the use of the apparatus the shot point may be represented on the zero depth line a at, say, b, and the receiving instruments by points such as 0. These may be grouped, for example, as indicated in Figure 1 to form a spread delineated by the downwardly drawn lines spaced as indicated at d. If this spread is used constantly for a whole set of readings, the blocks [0 and I2 are adjusted on the rod l4 so that the spacing between the pivots and 32, i. e., between the edges 34 and 36 will correspond to the extent of this spread, which as indicated above, may be of the order of 2,000 to 3,000 feet. With this adjustment having been made, the edge 34 may be lined up with the end instrument of the spread nearest the shot point and the edge 36 with the end instrument of the spread furthest from the shot point, and theblocks then located in position in the head. The screws 42 and 46 are then freed and the slide 40 is adjusted along the arm 26 until its index mark 41 is adjacent the calculated travel distance of a reflection recorded by the instrument nearest the shot point, and the slide 40 is then clamped on the arm 26. The arms 26 and 28 are then oscillated about their pivots 30 and 32 until the mark 41 on the slide 44 is in line with the value on arm 44 corresponding to the calculated travel distance of the same reflection farthest from the shot point. The slide 44 is then locked and the pin 50 depressed to form a puncture in the graph sheet. The procedure just described is then repeated for other reflections recorded with the same shot point and recording set-up. Following this the clamp screws 20 and 22 may be freed and the assembly moved to the position of other instruments on which records were made using the same shot point and the process repeated. The same process may also be repeated for different shot points and different instrument set-ups, the spacings between the paths 30 and 32 being adjusted if nec.- essary.

It is obvious that a systematic use of the instrument makes it possible to chart a large amount of observational data within a short period of time. It will be noted that the arms 26 and 28 are respectively parallel to lines joining the pivot 30 and the pin 50 and the pivot 32 and the pin 50. The instrument can be used with the shot point on either side of the recording instrument.

The significance of what is done by the use of the instrument may be best made clear by considering what is produced when there is a single shot point at b and a number of instrument set ups along the line a. Suppose that with this shot point and a series of instrument set-ups along the line a the marks of the pin 50 lie at various points along a line such as e. Consider first the significance of the mark made at f, the position of the pin 50 illustrated in Figure 1. If perpendicular to the line at its center 9 there is erected a perpendicular to bf as indicated at gh, then the lines drawn from pivot 30 to 50 and 32 to 50, respectively, will intersect gh at m and n, respectively, the points at which reflection took place to give rise to the observed data on the assumption that the reflecting points lay in a perpendicular plane through the shot point and the instruments. This assumption is, of course, always macle preliminarily. The significance of the point f, it will be readily seen, is that it is the image point of the shot point with respect to the points 30 and 32. The line mn then represents the portion of the reflecting boundary from which the particular reflection occurred. By taking account of other image points such as f, other portions of the boundary such as mn from which reflections occurred may be determined. The complete trace of the reflecting boundary in the perpendicular plane through the shot point and the instruments will then be the locus defined by the lines such as mn and m'n'. Some correction may, of course, have to be made if other arrays of the instruments indicate that the boundary sloped in a direction transverse to the vertical plane through the. shot point and the instruments.

The apparatus, of course, does not plot automatically all of this data, but serves to give readily the image points such as f which, to those skilled in the art, give very considerable information.

What I claim and desire to protect by Letters Patent is:

1. Apparatus for the solution of problems arising in seismographic prospecting comprising means providing a track, a pair of slide members movable along the track, means for maintaining said slide members in fixed relation to each other during such movements, an arm pivoted to each of said slide members and adapted to extend over a surface to which said track is parallel, and means adjustably pivotally joining said arms in converging relationship.

2. Apparatus for the solution of problems arising in seismographic prospecting comprising means providing a track, a pair of slide members movable along the track, an arm pivoted to each of said slide members and adapted to extend over a surface to which said track is parallel, elements adjustable along said arms, and means for pivotally joining said elements.

3. Apparatus for the solution of problems arising in seismographic prospecting comprising means providing a track, a pair of slide members movable along the track, means for mainf taining said slide members in fixed relation to each other during such movements, an arm pivoted to each of said slide members and adapted to extend over a surface to which said track is paral-. lel, elements adjustable along said arms, and means for pivotally joining said elements.

4. Apparatus for the solution of problems arising in seismographic prospecting comprising means providing a track, a pair of slide members movable along the track, an arm pivoted to each of said slide members and adapted to extend over a surface to which said track is parallel, means adjustably pivotally joining said arms, and means for marking on said surface the point at which said arms are pivotally joined.

JOHN F. ANDERSON. 

